Airplane with variable-incidence wing

ABSTRACT

The craft is for hovering flight, vertical takeoff and landing, and horizontal forward flight. It has a tail-sitting fuselage and a ducted fan mounted to the fuselage aft to provide propulsion in both (a) hovering and vertical flight and (b) horizontal forward flight. At each side is a floating wing, supported from the fuselage for passive rotation (or an actuator-controlled optimized emulation of such rotation) about a spanwise axis, to give lift in forward flight. The fuselage attitude varies between vertical in hovering and vertical flight, and generally horizontal in forward flight. Preferably the fuselage is not articulated; there is just one fan, the sole source of propulsion, rotating about only an axis parallel to the fuselage; and thrust-vectoring control vanes operate aft of the fan. Preferably at each side a small, nonrotating wing segment is fixed to the fuselage, and the floating wing defines--along its trailing portions--a corner notch or slot near the fuselage; forward portions of the fixed wing segment are within this notch. Preferably the spanwise axis is along a surface of the floating wing, and a long hinge supports that wing from the fixed wing segment, within the notch. During vertical and transitional flight characteristically the leading edge of the floating wing is down relative to the fuselage axis.

.Iadd.This application is a continuation of application Ser. No.08/195,247 filed Feb. 14, 1994 which is a Re of 07/308,655 filed Feb. 9,1989, now U.S. Pat. No. 5,086,993. .Iaddend.

BACKGROUND

1. Field of the Invention

This invention relates generally to vertical-takeoff-and-landing (VTOL)airplanes; and more particularly to tail-sitting aircraft capable ofhovering flight, generally vertical takeoff and landing, andsubstantially horizontal forward flight.

2. Prior Art

Two types of prior aircraft are pertinent to my invention:

ducted -fan craft, such as the French Coleopter (FIG. 8) and the 1972Shorts Skyspy; and

"free wing" or "floating wing" craft in which the wing pivots about aspanwise axis, and is free to float in response to gusts. FIGS. 9through 12 show a craft of this type, designed by Spratt.

In operation near hover, for a given diameter and power, a ducted fanproduces more static thrust than an unducted propeller. The Coleopterenjoys this important advantage. Following is an excerpt from Taylor, J.W. R., ed., Jane's Pocket Book of Research & Experimental Aircraft(1976), at page 221, on the "SNECMA C.450-01 Coleopterere". FIG. 8 hasbeen adapted from page 220 of the same work.

"Power plant: One SNECMA Atar 101E V turbojet engine (8,157 lb. 3,700 kgst).

"Diameter of wing: 10 ft 6 in (3.20 m).

"Length: 26 ft 31/2 in (8.022 m).

"Accomodation: Pilot only.

"Special design features: Annular wing of light alloy construction,consisting of two skins and internal structure (chord 9 ft 10 in, 3.0m). Retractable foreplanes in fuselage nose. Cruciform fins and ruddersto provide directional control in all axes. Four oleo-pneumatic landinglegs mounted on trialing-edge of wing, small castoring wheels withrubber tyres. Tilting pilot's seat which could be ejected in anemergency.

"History: Initial tests with the `Atar Volant` pilotless and pilotedtest vehicles proved the ability of a vertically-mounted turbojet toraise a VTOL aircraft safely from the ground, to accelerate it isvertical flight to a speed where it could become airborne like aconventional aircraft, and to return it to the ground in a verticaldescent. SNECMA then built a prototype research aircraft around thistype of power plant. Known as the C.450-01 Coleoptere, this prototypewas basically similar to the C.400 P-3 piloted `Atar Volant`, but wasfitted with an annular wing to permit transition into horizontal flight.The airframe, built by the Nord company in its Chatillonsous-Bagneuxworks, was intended for tests at subsonic speeds. Directional control attake-off and landing was by pneumatic deflection of the main jet efflux,directional control during normal horizontal flight was by fourswiveling fins equally spaced around the rear of the annular wing. Underan agreement signed in 1958, the Federal German Ministry of Defencecollaborated with SNECMA in this research programme. The C.450-01 madethe first free vertical flight on May 6, 1959 at Melun-Villaroche, buton July 25, during a transition from vertical to horizontal flight,control of the aircraft was lost and it crashed from 250 ft (75 m).Although the aircraft was destroyed the pilot ejected successfully.Testing the Coleopiere, however, was considered to have been successfuldespite the accident."

In cruise, the Coleopter is handicapped by having a wingspan that issmall (i.e., equal to the duct diameter). This small causes span thecruise induced drag (drag due to lift) to be unacceptably high.

Several free-wing aircraft have been proposed and built. I do not knowof any that have claimed static-thrust capability, although a brochureof the Allen Aircraft Company does describe an aircraft with capabilityof takeoff and landing over short distances. Excerpts (not necessarilyin their original order) follow.

"The GEMINI TURBOPROP-350 is a new, innovative, single-engine, specialperformance aircraft. The GTP-350 is powered by Allison'ssoon-to-be-certified turbine, the 225-B10, delivering 350 shaft horsepower (SHP). Combining the 225-B10 with the low weight, high strengthcharacteristics of Allied's SPECTRA and COMPET Fibers creates ahigh-performance state-of-the-art aircraft. What really sets the GTP-350apart, however, is the patented Slaved Tandem Freewing design; thisconfiguration provides dramatic safety improvements as well as givingthe plane near vertical take-offs and landings (VTOL). This brochuretells the story of the revolutionary GEMINI TURBOPROP-350. . . .

"SPECIFICATIONS

"The fully acrobatic GTP-350 is designed for multi-mission applications.Proposed applications include training such as high maneuverabilityaerial combat; high performance off-airport operations such as medicaland other evacuation from remote areas; close support of combat troopswith helicopter-like performance; border patrol, reconnaissance,agricultural and wide area land management missions and general purposeuse. The GTP-350, presently available without an FAA certificate (aseither a kit or an exempt airplane), is excepted to receive FAA Part 23certification. Allen Aircraft Company presently has production capacityfor 10 GTP-350s per year. Substantial contribution to the developmenteffort was made by Allison Division or General Motors Corporation. . . .

    ______________________________________                                        "DIMENSIONS, EXTERNAL                                                         Wing span              38.33   ft.                                            Chord at root          5.83    ft.                                            Chord at tip           3.83    ft.                                            Mean Aerodynamic Chord 5.45    ft.                                            Wing Aspect Ratio      7.60                                                   Wing taper ratio       0.67                                                   Sweep                  4.00    deg.                                           Length overall         20.54   ft.                                            Fuselage: max width    4.50    ft.                                            max depth (excluding ascelle)                                                                        4.20    ft.                                            Height overal          9.38    ft.                                            Rear wing span         25.33   ft.                                            Rear wing chord at root                                                                              3.83    ft.                                            Rear wing chord at tip 2.33    ft.                                            Wheel track            8.33    ft.                                            Wheel base             5.33    ft.                                            Propeller diameter     85.0    inches                                         Propeller ground clearance                                                                           2.28    ft.                                            "DIMENSIONS, INTERNAL:                                                        Cabin:                                                                        max length             9.80    ft.                                            max width              3.41    ft.                                            max height             3.50    ft.                                            "AREAS:                                                                       Wings, gross           187.72  sq. ft.                                        Ailerons, total        33.68   sq. ft.                                        Exposed vertical fin   41.43   sq. ft.                                        Rudder                 9.23    sq. ft.                                        Rear wings, gross      78.48   sq. ft.                                        "WEIGHTS and LOADINGS:                                                        Basic weight empty (typical equipment)                                                               754     lbs.                                           Maximum take-off weight (aerobasic)                                                                  1500    lbs.                                           Maximum take-off weight (utility)                                                                    2200    lbs.                                           Fuel, max capacity     700     lbs.                                           Maximum wing loading   11.5    lbs./sq. ft.                                   Maximum power loading  6.28    lbs./shp                                       "PERFORMANCE:                                                                 Never exceed speed     230     mph                                            Maximum level speed at sea level                                                                     190     mph                                            75% normal cruise      173     mph                                            Minimum level speed, no vectored thrust                                                              70      mph                                            Minimum controllable speed,                                                                          20      mph                                            full thrust vectoring                                                         Maximum sustainable climb angle                                                                      90      degrees                                        Maximum climb rate at sea level                                                                      3520    fpm                                            Take-off run, no vectored thrust                                                                     1200    ft.                                            Take-off run, full thrust vectoring                                                                  75      ft.                                            Landing roll out, no vectored thrust                                                                 600     ft.                                            Landing roll out, full thrust vectoring                                                              65      ft.                                            Service ceiling        25,000  ft.                                            Range with 45 min. reserves                                                                          800     n.m.                                           g limits, max aerobatic TOW                                                                          +6/-3                                                  g limits, max utility TOW                                                                            +4.4/-2.2                                              ______________________________________                                    

HISTORY OF THE GEMINI TURBOPROP-350 PROJECT

"The GEMINI TURBOPROP-350 (GTP-350) lineage began prior to World War IIwhen George K. Spratt and Daniel R. Zuck independently invented pure`freewing` design aircraft. Spratt, the more active researcher or thetwo, has designed, built and flown more than a dozen freewing vehicles.Further development came in the 1950s and 60s when several otherresearchers--including teams from NASA, General Dynamics and BattelleMemorial Laboratories [--] reported the study, building and successfulflying of freewing designs. "In early 1977, Edward H. Allen, Ph.D., aprofessional systems scientist and experienced pilot, began to examinefreewing development and perform experiments that eventually led to theformulation of a new concept--the `Slaved Tandem Freewing` (STF)configuration. Dr. Allen believed that theoretically the newconfiguration could be shown to be 10 times safer than existing generalaviation aircraft. As a result, when the U.S. Department ofTransportation requested proposals in 1984 for innovative means toreduce accidents and increase the safety of vehicles, Dr. Allensubmitted a proposal for developmental funding of the STF design. Afeasibility study contract was awarded by the DOT and after evaluatingthe results of that study, a two-year, follow-on contract for additionaldevelopment work was awarded--including the design, manufacture andtesting of a manned prototype. The DOT-sponsored work included thetesting of four subscale, remotely piloted research vehicles (RPRVs . ..)--the largest of which had a 17-foot wing span and weighed more than100 pounds. The [RPRVs] served to demonstrate the concept and the GEMINITURBOPROP-350 was born.

"Construction of the full-scale manned prototype began early in 1987.Flight testing is scheduled to begin with ground tests and systemcheck-out in October 1987, with the first flight the following month.

"THRUST VECTORING: THE SECRET TO NEAR VTOL

"The GEMINI TURBOPROP-350 is the world's first aircraft to offer nearvertical takeoff and landing performance without the mechanicalcomplexity of a helicopter--and without losing high speed performance.The unique STF configuration allows the pilot to control deck angleindependent of the wing's angle of attack. By rotating the fuselage to ahigh angle of attack while leaving the wings in a level flight attitude,the pilot is able to direct or `vector` the thrust. The benefit of this`extreme flair [sic]` landing and takeoff maneuver is the ability tooperate from confined areas with little takeoff run and even lesslanding roll.

"SAFETY-THE VALUE OF THE STF CONCEPT

"Ease of operation and inherent safety in vehicle design are thegreatest strengths of the STF concept. Of primary importance is the factthat STF vehicles cannot be stalled or spun in the dramatic way thatfixed wing aircraft can. In addition, the natural tendency of an STFsystem to reduce the shocks from sudden changes in wind direction--the`gust allevation` tendency--is as important as stall resistance. Inaerodynamic vehicles, the freewing is comparable to an automobile'ssuspension system . . . : it provides a safe and comfortable flight."

A related prior aircraft, the Spratt/Stout Skycar, is shown in FIG.13--which is adapted from Bowers, Unconvenional Aircraft (1984), page195. The accompanying test at pages 194 and 195 of that same workfollows.

"Spratt Wing/Stout Skycar IV

"Since 1930, famous American designer William B. Stout had been tryingto develop an easy-to-fly `everyman's airplane` through his series ofSkycars. At the end of World War II he teamed up with George Spratt ofthe Stout Research Division or Convair, who had been developingairplanes with movable wings for several years. The Spratt/Stoutcollaboration, identified as Skycar IV, was built by Convair when thatfirm became interested in flying automobiles in 1946.

"The Spratt wing was similar to that of the Mignet Flying Flea in beingthe primary pitch control for the airplane, but did much more in that itwas also pivoted in such a way that it could be banked to put the planein a turn. The wing was mounted above an elongated auto-like body with aburied engine driving a pusher propeller at the rear through anextension shaft [see FIG. 13]. The fixed end finds were used forstability only, not control. With the movable wing, there was no needfor elevators, rudder, or ailerons.

"This proof-of-concept prototype concentrated more on the aerodynamicdetails than the automotive. Although this one, for which technical datais conspicuously absent, was abandoned, Mr. Spratt is still developingaircraft with his wing at this writing."

Allen's and Spratt's craft are relatively complex in that each requiresa separate horizontal tail. Moreover, neither is intended to hover. Thewing bending moments are carried on a shaft; this wastes weight, becausethe shaft must be relatively large and heavy.

SUMMARY OF THE DISCLOSURE

A first preferred embodiment of my invention is an aircraft for hoveringflight, generally vertical takeoff and landing, and substantiallyhorizontal forward flight. It includes a fuselage that has a generallylongitudinal axis.

It also includes some means for standing the aircraft for verticaltakeoff and landing, with the fuselage axis substantially vertical, on alanding surface. For generality and breadth of expression I shall referto these means as the "support means".

This preferred embodiment also includes some means for propelling theaircraft in both (a) hovering and vertical flight and (b) substantiallyhorizontal forward flight. These means comprise at least one ducted fan,and--again for generality and breadth--I shall call them the "ducted-fanmeans" or simply the "fan means". The fan means are supported from thefuselage aft.

This preferred embodiment must also include some means, comprising atleast one floating wing, for providing lift in forward flight. Thesemeans--once again for generality the "floating-wing means"--aresupported from the fuselage, at each side or the fuselage, for passiverotation about a generally spanwise axis.

The fuselage-axis attitude varies between substantially vertical inhovering and vertical flight, and generally horizontal in forwardflight.

The foregoing may be a description of the first preferred embodiment ofmy invention in its most general or broad form. From what has alreadybeen stated, it can now be appreciated that my invention resolves theabove-noted fundamental in adequacies of the prior art.

In particular, as compared to prior free-wing configurations of, e.g.,Spratt and Stout, my invention shares the advantages of the Coleopter'sducted fan--namely, the very high level of available static thrust thatis of enormous value for efficient VTOL and hover operation, and alsothe greater safety of the guarded fan. On the other hand, by adding awing that can be of far greater span than the duct diameter, myinvention provides induced-drag levels comparable with those of aconventional airplane configuration--and thus is vastly superior incruise performance to all prior flying-duct craft. Added safetyadvantages accrue from the stall resistance of the floating wing.

As will be appreciated, however, I prefer to contemplate practice of myinvention with certain additional characteristics or features thatprovide the fullest enjoyment of its potential benefits and advantages.

For example, the fuselage is preferably substantially unarticulated, atleast between (1) an attachment location of the floating-wing means tothe fuselage and (2) the fan means. Preferably the fuselage issubstantially unitary and unarticulated--i.e., along its entire length.

As another example, I prefer that the fan means comprise exactly one fan(which may be a contrarotating fan), of adequate size for efficientoperation in hovering flight; and that the fan be substantially the onlymeans of propulsion in vertical takeoff and landing, hover, and forwardflight.

In this latter case I prefer that the fan means also comprise agenerally cylindrical duct surrounding the fan and generally surroundingan aft segment of the fuselage; and some means for vectoring thrustdeveloped by the fan. These "thrust-vectoring means" (considered as aunit) are fixed relative to the fuselage.

I also prefer that the thrust-vectoring means comprise a plurality ofdeflection vanes, each mounted for rotation about a respective axis. Theaxis of rotation of each vane is fixed in relation to the fuselage andthe duct, aft of the fan. Full control capability for hover is providedby use of these movable vanes located near the duct exit.

In addition I prefer that the fan be fixed, relative to the fuselage,for rotor rotation about exclusively an axis substantially parallel tothe fuselage axis. I also prefer to include a mechanical stop forlimiting passive rotation of the wing to an attitude suited for rapidforward flight.

I further prefer that the spanwise axis of rotation of the floating-wingmeans be along a surface of the wing; and that this embodiment of myinvention further comprise a long hinge supporting the floating-wingmeans for rotation about the spanwise axis. The spanwise axis ispreferably along a lower surface of the wing.

Thus, compared with the Allen or Spratt craft, the "break" in the wingis arranged differently--in such a way that wing bending moments areresisted by the long hinge, instead or being carried on a single shortshaft. This saves weight, since the hinge pin can be made smaller andlighter than a shaft.

Moreover I prefer that this embodiment of my invention also comprise, ateach side of the fuselage, a wing segment that is fixed to the fuselageagainst rotation. In this case the floating-wing means preferablydefine, along trailing portions thereof, a corner notch or slotgenerally near the fuselage; and forward portions of the fixed wingsegment are preferably disposed within that slot in the floating wing.

In a second preferred embodiment of my invention, the aircraft isfurther expressly understood to be also for transitional flight betweenvertical and horizontal flight. The fan means propel the craft invertical, horizontal and transitional flight.

The wing is supported for rotation as in the first embodiment; but asfurther explained below this rotation is not necessarily passive. Inthis embodiment, during vertical and transitional flight the leadingedge of the wing is down relative to the fuselage axis.

A third preferred embodiment of my invention is comparable to thesecond, except that the leading-edge-down condition is not necessarilysatisfied. Instead it is expressly understood that the rotating wingprovides lift in transitional as well as horizontal flight and that thewing incidence in transitional flight is substantially always within asmall range of angles of attack with respect to an oncoming airstream.

As to the second and third embodiments, I prefer that the wing incidencebe controlled by actuators, at least during transitional flight; andthat the actuators be scheduled by a flight-control system. Advantagesof these embodiments will become more clear from the detaileddescription that follows.

All of the operational principles and advantages of the presentinvention will be more fully appreciated upon consideration of thefollowing detailed description, with reference to the appended drawings,of which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a preferred embodiment of my inventionin its tail-sitting orientation, but showing the rotatable wing angledrelative to the fuselage as for transitional flight.

FIG. 2 is a like view of the FIG. 1 embodiment, but with the wingaligned with the fuselage as for generally horizontal cruising flight.

FIG. 3 is a perspective view of the same embodiment with the fuselageoriented horizontally, also as for generally horizontal cruising flight.

FIG. 4 is an elevation of the same embodiment in its tail-sittingorientation, viewing the broad surfaces of the wing substantiallystraight on--i.e., from the viewpoint that would be above the craft ifit were in flight.

FIG. 5 is a plan view or the same embodiment, still in a tail-sittingorientation--i.e., a view that would correspond to a front elevation ofthe craft, if it were in flight.

FIG. 6 is an elevation of the same embodiment, similar to FIG. 4 buttaken viewing the wing at one side of the craft edge on--i.e., from theviewpoint that would be at one side of the craft if it were in flight.

FIG. 7 is a composite elevation showing the craft--very diagrammaticallyor schematically--in successive stages of operation from tail-sittingposition for takeoff through ascending transition, cruise, anddescending transition into a tail-sitting landing.

FIG. 8 is an elevation (after Taylor, supra, at 220) of the prior-artColeopter with its special truck-mounted hoist.

FIG. 9 is a perspective view (after promotional literature of the AllenAircraft Company) of the prior-art Gemini Turboprop-350 (understood tobe a trademark of that firm) in an environment characteristic of thatcraft's short takeoff-roll and short landing-rollout distances.

FIG. 10 is a diagrammatic side elevation (ibid.) of the same prior-artcraft in a preliminary takeoff-roll or landing-rollout orientationwherein the fuselage is generally horizontal.

FIG. 11 is a like view (ibid.) of the same craft in a later stage oftakeoff roll, in which the fuselage is oriented steeply upward.

FIG. 12 is a front elevation (ibid.) of the same craft in its FIG. 10orientation.

FIG. 13 is a perspective view of the Spratt Wing/Stout Skycar IV (afterBowers, supra, at 195).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

1. General Configuration and Operation

The configuration of my contemplated vehicle is shown in FIGS. 1 through6. Thrust is provided by an aft-mounted, ducted 22, preferablycontrarotating fan 21 (FIG. 4). Vanes 25 in the fan efflux providecontrol about all three axes in cruise as well as when the vehicle ishovering.

The wing 31 is pivoted along an approximately spanwise axis 24 (FIG. 1),allowing the wing to vary in angle of attack. There are at least threewing-incidence control options:

fully-floating wing;

floating wing which couples with body or fuselage 11 incidence at lowangles of attack; and

wing incidence controlled by actuators and scheduled by a flight-controlsystem.

In the first of these options, the combination of hinge axis 24 and wingpitching-moment coefficient at zero lift are tailored so that the wingtends to float at a lift coefficient near the maximum value.

In the second option, stops are arranged so that the wing may only floatleading-edge-down relative to the body. These stops, in conjuction withthe floating characteristics just mentioned, cause the wing and body toremain coupled as long as the body angle of attack is lower than thetrimmed floating angle of attack of the wing (typically about fifteendegrees).

In this mode, the vehicle flies and maneuvers like a conventional, rigidairplane. At body angles of attack in excess of the wing trimmedfloating angle of attack, the wing decouples from the body and floats atits designed angle of attack.

In the third option the incidence angle can be programmed for variousobjectives. (For example, it may emulate either of the first two optionsbut with optimized dynamic response.)

Lateral (roll) control options include at least these:

spoilers on outboard wings;

ailerons which are locked out when the wing is floating;

ailerons scheduled by a flight-control system such that they controlwing incidence when the wing is floating and operate in the same manneras conventional ailerons when the wing is locked:

differential variation of wing incidence about a "tilting" hinge axis;and

all roll control by differential deflection of vanes 25 in the fan duct.

Antitorque control possibilities include at least these threestrategies:

dual-rotation fans 21 (FIG. 4)--i.e., a contrarotating fan;

a single-rotation fan plus antitorque stator vanes; and

an antitorque rotor or reaction-control antitorque system.

Note from FIGS. 1 through 4 the wing segment 23 that is fixed to thefuselage 11 against rotation, and structurally integrated with the duct22--very firmly securing the duct to the fuselage. As is clear from theillustrations, some forward portions of this fixed wing segment 23 aredisposed within a corner notch or slot 32 that is formed in the rotatingwing 31, generally near the fuselage.

2. Transition and Conversion

FIG. 7 illustrates the transition and conversion process. Fordefiniteness the following discussion is in terms of the secondwing-incidence control option, though as will be understood the processmay be described equally straightforwardly for the other two.

Transition from takeoff or hover 41 to cruise 43 is accomplished byprogressively tilting the body 11 from the vertical. As forward speedbuilds, the floating wing develops progressively more lift--allowing thebody 11 and fans 21 to nose down, which increases the forward componentof thrust and decreases the lift component of thrust.

When the body angle of attack decreases to the wing floating angle ofattack, the wing and body couple. The vehicle then flies in the mannerof a conventional rigid airplane.

Conversion from cruise to hover or landing 46 begins with a steady,one-g, wing-borne deceleration. When the airspeed falls to the pointthat the wing is flying at its designed floating lift coefficient inorder to support the aircraft in level flight, the body angle of attackequals the trimmed float angle of attack of the wing.

As deceleration proceeds, the body rotates to a more nose-up attitude44, 45 and the wing decouples from the body and remains floating at itstrimmed angle of attack. This allows the vehicle to fly at body anglesof attack above the stall angle of attack of the wing without stallingthe wing.

When the body and duct angle of attack pass through the criticalduct-flow separation angle-of-attack range (typically thirty to fortydegrees), the wing is still generating considerable lift--unloading thefans and duct, and greatly decreasing duct buzz or flow separation.Conversion from wingborne flight to hover is accomplished byprogressively nosing up the body until it is oriented vertically 46.

The wing floats at its designed angle of attack throughout theconversion 44, 45. This allows a progressive transfer of lift from thewing to the fans as the vehicle decelerates.

3. System Simplicity

The tilt-body craft is much simpler than other VTOL vehicles. Itrequires almost no additional systems besides the wing hinges 24 (at theunderside of the wing, FIG. 1) and the duct to give an otherwiseconventional plane VTOL capability.

The same propulsion system is used for powered lift and cruisepropulsion. There is no need for cross-shafting, rotor-tilt actuatorsand systems, or angle-drive gearboxes.

The fans 21 may be made fixed-pitch, although they are no more complexthan conventional variable-pitch propellers in any case. There is noneed for cyclic pitch-control mechanisms. Control in both hover andcruise is provided by at least three stator vanes 25 mounted in the fanefflux.

In cruising flight the vanes 25 merely replace the elevators, rudder andailerons of a conventional airplane. In VTOL and hover the same vanesperform the functions normally associated with cyclic pitch andtail-rotor variation for a conventional helicopter.

The tilt-body therefore requires no more control actuators than aconventional airplane. The control system can be quite simple, since allof the controls operate in the same sense in cruise and hover.

4. Operational Advantages

For operations from confined areas 29 (FIG. 1) and aboard ships, thetilt-body offers a large improvement in ease of handling and safety overprior aircraft, including prior remotely-piloted vehicles (RPVs). TheVTOL capability of the craft allows it to be launched and recoveredwithout special equipment such as catapults, JATO bottles or recoverynets.

The ducted propulsion system is fully enclosed. Unlike the rotors of ahelicopter or tilt-rotor vehicle, it poses little threat to nearbypersonnel.

Incorporation of the floating wing gives the tilt-body a much widertransition corridor than either fixed-wing tail-sitting vehicles or pure"flying duct" vehicles such as the SkySpy, or the Coleopter. The wingalso gives the tilt-body a far lower span-loading and hence greatlyimproved altitude and loiter performance than a "flying duct" vehicle.

Hover performance of the tilt-body lies between that of alow-disc-loading vehicle like a helicopter or tilt-rotor craft and ahigh-disc-loading vehicle like a vectored-thrust jet-lift craft.Incorporating the duct 22 improves hover efficiency. Unlike atilt-rotor, the tilt-body does not suffer from rotor-induced downloadson the wings.

5. Performance

The combination of sufficient power to hover with a clean, low-dragairframe yields exceptional performance in horizontal flight. Based oncomputer modeling, a preferred embodiment of my invention can fly atsustained altitudes up to 40,000 feet and has a sea-level top speed of248 knots. The combination of high speed and VTOL capability give thetilt-body the ability to provide quick response, particularly when theVTOL capability is exploited to allow forward basing.

Following is a calculated performance summary for a preferred embodimentof my tilt-body vehicle that is described by the specificationsindicated.

    ______________________________________                                        BASELINE SPECIFICATIONS                                                       ______________________________________                                        control type      RPV                                                         span              15 feet                                                     area              32 square feet                                              span efficiency   0.850                                                       aspect ratio      7.03                                                        weight            430 pounds                                                  fuel fraction     0.1                                                         power             150 shaft horsepower                                        fan diameter      4 feet                                                      prop efficiency   0.900                                                       payload           134 pounds                                                  ______________________________________                                        BASELINE PERFORMANCE                                                          drag buildup                                                                  parasite drag buildup                                                         ______________________________________                                        fuselage D/Q           0.10000                                                wing D/Q               0.32000                                                empennage D/Q          0.37000                                                gear D/Q               0.00000                                                additional D/Q         0.00000                                                interference           0.04740                                                total airplane         0.83740                                                CD minimum             0.026                                                  C.sub.D /C.sub.L.sup.2 0.053                                                  L/D maximum            13.39                                                  C.sub.L at L/D maximum 0.700                                                  ______________________________________                                        CRUISE PERFORMANCE                                                                         at altitude (feet)                                               parameter      0         20.000   40.000                                      ______________________________________                                        minimum power (THP)                                                                          6.50      8.91     13.11                                       maximum engine power                                                                         150.0     72.9     25.6                                        (SHP)                                                                         maximum speed (KTAS)                                                                         248.7     239.2    200.8                                       75% cruise (KTAS)                                                                            225.7     215.9    169.7                                       C.sub.L at 75% power                                                                         0.078     0.159    0.550                                       cruise                                                                        maximum rate of climb                                                                        5,386.01  2,403.50 355.01                                      (FPM)                                                                         climb power (THP)                                                                            89.8      45.3     18.7                                        climb C.sub.L  0.2500    0.4500   0.8000                                      climb speed (KTAS)                                                                           126.1     128.7    142.0                                       climb gradient 0.42220   0.18452  0.02470                                     1-g wing-dccouple speed                                                                      57.5      78.8     116.0                                       (KTAS)                                                                        best climb gradient                                                                          0.65354   0.23871  0.023539                                    best angle-of-climb                                                                          57.5      78.8     133.9                                       speed (KTAS)                                                                  loiter endurance (hours)                                                                     12        9.5      6                                           ______________________________________                                        HOVER PERFORMANCE                                                             at sea level                                                                  ______________________________________                                        figure of merit        0.60                                                   static thrust (pounds) at maximum power                                                              485                                                    thrust/weight ratio at 1.12                                                   maximum power and gross weight                                                                       25                                                     hover endurance (minutes)                                                     ______________________________________                                    

6. System Development

The information presented in this document is believed lo be sufficientto enable persons of ordinary skill in the art of aircraft developmentto practice my invention--i.e., to refine the design and build thecraft--in a generally routine fashion. Some of the steps contemplatedfor such development are discussed below.

The till-body craft would benefit from both force-balance-mountedwind-tunnel testing and free-flying tests. The latter would beparticularly useful in defining the aircraft transition corridor and inrefining control strategies for hovering and transition. In either case,power effects are sufficiently dominant that testing must be done with apowered model.

The tilt-body aircraft could be demonstrated by constructing and flyinga scaled-down radio-controlled model of the proposed operationaltilt-body vehicle. Flight-testing of the model would demonstrate thecontrollability of the vehicle over its entire night envelope, includinghover, transition and conversion.

It will be understood that the foregoing disclosure is intended to bemerely exemplary, and not to limit the scope of the invention--which isto be determined by reference to the appended claims.

I claim:
 1. An aircraft for hovering flight, generally vertical takeoffand landing, and substantially horizontal forward flight, comprising:afuselage having a generally longitudinal axis; support means forstanding the aircraft for vertical takeoff and landing, with thefuselage axis substantially vertical, on a landing surface; ducted-fanmeans, supported from the fuselage aft, for propelling the aircraft inboth (a) hovering and vertical flight and (b) substantially horizontalforward flight; and at each side of the fuselage, floating-wing means,supported from the fuselage for passive rotation about a generallyspanwise axis, for providing lift in forward flight; wherein thefuselage-axis attitude varies between substantially vertical in hoveringand vertical flight, and generally horizontal in forward flight.
 2. Theaircraft of claim 1, wherein:at each side of the fuselage, thefloating-wing means are supported from the fuselage at an attachmentlocation; and at least between the wing-means attachment locations andthe fan means, the fuselage is substantially unarticulated.
 3. Theaircraft of claim 1, wherein:the fuselage is substantially unitary andunarticulated.
 4. The aircraft of claim 1, wherein the fan meanscomprise:exactly one fan, of adequate size for efficient operation inhovering flight; said one fan being substantially the exclusive means ofpropulsion for the aircraft in vertical takeoff and landing, hover, andforward flight; a generally cylindrical duct surrounding the fan andgenerally surrounding an aft segment of the fuselage; and means, fixedin relation to the fuselage, for vectoring thrust developed by the fan.5. The aircraft or claim 4, wherein:the thrust-vectoring means comprisea plurality of deflection vanes, each mounted for rotation about arespective axis that is fixed in relation to the fuselage and the duct,aft of the fan.
 6. The aircraft of claim 4, wherein:the fan is fixed,relative to the fuselage, for rotor rotation about exclusively an axissubstantially parallel to the fuselage axis.
 7. The aircraft of claim 1,wherein:the ducted-fan means comprise:a fan, and a generally cylindricalduct surrounding the fan, and generally surrounding a segment of thefuselage; and the floating-wing means extend outboard beyond the duct.8. The aircraft of claim 7, wherein:the outboard extension or thefloating-wing means beyond the duct is larger than the duct diameter. 9.The aircraft of claim 7, further comprising:at each side of thefuselage, a wing segment fixed to the fuselage against rotation; whereinthe floating-wing means define, along trailing portions thereof, acorner notch or slot generally near the fuselage; and wherein forwardportions of the fixed wing segment are disposed within the notch or slotin the foaling wing.
 10. The aircraft of claim 9:wherein the spanwiseaxis is along a surface of the wing; and further comprising a long hingesupporting the floating-wing means from the fixed wing segment, withinthe notch or slot, for rotation about the spanwise axis.
 11. Theaircraft of claim 1:wherein the spanwise axis is along a surface of thewing; and further comprising a long hinge supporting the floating-wingmeans for rotation about the spanwise axis.
 12. The aircraft of claim11, wherein:the spanwise axis is along a lower surface of the wing. 13.The aircraft of claim 1, further comprising:a mechanical stop forlimiting passive rotation of the wing to an attitude suited for rapidforward flight.
 14. An aircraft for generally vertical flight intakeoff, hover and landing, substantially horizontal cruising flight;and transitional flight between vertical and horizontal flight; saidaircraft comprising:a fuselage having a generally longitudinal axis;support means for standing the aircraft for vertical takeoff andlanding, with the fuselage axis substantially vertical, on a landingsurface; ducted-fan means, supported from the fuselage aft, forpropelling the aircraft in vertical, horizontal and transitional flight;and at each side of the fuselage, a wing supported from the fuselage forrotation about a generally spanwise axis, substantially for providinglift in forward flight;wherein the fuselage-axis attitude fortransitional flight varies between substantially vertical in verticalflight, and generally horizontal in horizontal flight; and whereinduring vertical and transitional flight the leading edge of the wing isdown relative to the fuselage axis.
 15. The aircraft of claim 14,wherein the wing is supported from the fuselage for rotation about saidaxis, between:a leading-edge-down attitude with respect to the fuselage,in vertical and transitional flight; and a substantially conventionalattitude with respect to the fuselage, in cruising forward flight. 16.The aircraft of claim 15, wherein:the substantially conventionalattitude is leading-edge-up with respect to an oncoming air stream. 17.The aircraft of claim 15, wherein:in cruising forward flight, the wingis limited to the substantially conventional attitude by a positivemechanical stop.
 18. The aircraft of claim 15, wherein:the wing issupported for passive rotation relative to the fuselage, in vertical andtransitional flight; and is limited to the substantially conventionalattitude by a positive mechanical stop, in cruising forward night. 19.The aircraft of claim 15, further comprising:actuators for controllingincidence of the wing in transitional flight.
 20. The aircraft or claim14, wherein:the ducted-fan means comprise:a fan, and a generallycylindrical duct surrounding the fan, and generally surrounding asegment of the fuselage; and the wing extends outboard beyond the duct.21. The aircraft of claim 20, wherein:the outboard extension of the wingbeyond the duct is larger than the duct diameter.
 22. An aircraft forgenerally vertical flight in takeoff, hover and landing: substantiallyhorizontal crusing flight; and transitional flight between vertical andhorizontal flight; said craft comprising:a fuselage having a generallylongitudinal axis; support means for standing the aircraft for verticaltakeoff and landing, with the fuselage axis substantially vertical, on alanding surface; ducted-fan means, supported from the fuselage aft, forpropelling the aircraft in vertical, horizontal and transitional flight,and at each side of the fuselage, a wing supported from the fuselage forrotation, relative to the fan means and relative to the fuselage, abouta generally spanwise axis, the primary function of said wing beingprovision of lift in horizontal and transitional flight; wherein thefuselage-axis attitude in transitional flight varies betweensubstantially vertical in vertical flight, and generally horizontal inhorizontal flight; and wherein the wing incidence in transitional flightis substantially always within a small range of angles of attack withrespect to an oncoming airstream.
 23. The aircraft of claim 22, furthercomprising:means for maintaining the wing incidence, during transitionalflight, within said small range of angles of attack with respect to theoncoming airstream.
 24. The aircraft of claim 23, wherein:theincidence-maintaining means comprise actuators scheduled by aflight-control system.
 25. The aircraft of claim 22, wherein:theducted-fan means comprise:a fan, and a generally cylindrical ductsurrounding the fan, and generally surrounding a segment of thefuselage; and the wing extends outboard beyond the duct.
 26. Theaircraft of claim 25, wherein:the outboard extension of the wing beyondthe duct is larger than the duct diameter. .Iadd.
 27. An aircraft forhovering flight, generally vertical takeoff and landing, andsubstantially horizontal forward flight, comprising:a fuselage having agenerally longitudinal axis; a support arrangement for standing theaircraft for vertical takeoff and landing, with the fuselage axissubstantially vertical on a landing surface; a propulsion system,supported from the fuselage, for propelling the aircraft in both (a)hovering and vertical flight and (b) substantially horizontal forwardflight; and at each side of the fuselage, a floating-wing, supportedfrom the fuselage for passive rotation about a generally spanwise axis,for providing lift in forward flight; wherein the fuselage-axis attitudevaries between substantially vertical in hovering and vertical flight,and generally horizontal in forward flight. .Iaddend.